1. Field of the Invention
This invention relates to regulator circuits and, more particularly, to biasing of stacked power transistor devices within the regulator circuits.
2. Description of the Related Art
As complimentary metal oxide semiconductor (CMOS) device technology continues to advance, the device feature sizes continue to get smaller and the oxides continue to get thinner. These devices may be more susceptible to damage due to over voltage stressing. Accordingly, to prevent overstressing of these devices, they are typically used in applications with a reduced supply voltage. For example, devices manufactured using a typical 0.35 u CMOS process may only handle a supply voltage of approximately 3.3V. However, in many mobile devices such as mobile telephones, personal digital assistants (PDA), and the like, the typical battery voltage may range from 3.0V to 5.5V. Thus to directly use the battery voltage as a supply, designers are sometimes faced with either using devices manufactured with a high-voltage compatible process or to design the circuit to protect the low voltage devices from the high-voltage rail.